CA1332568C

CA1332568C - Cosmetic composition

Info

Publication number: CA1332568C
Application number: CA000610359A
Authority: CA
Inventors: Mavis Claire Pereira
Original assignee: Unilever PLC
Current assignee: Unilever PLC
Priority date: 1988-09-09
Filing date: 1989-09-05
Publication date: 1994-10-18
Anticipated expiration: 2011-10-18
Also published as: DE68916137T2; KR900004319A; US4981845A; AU622478B2; EP0358528B1; GB8821129D0; JPH02121906A; EP0358528A3; DE68916137D1; JPH0684291B2; ES2056220T3; EP0358528A2; AU4120689A; ZA896885B; ATE107160T1

Abstract

ABSTRACT

An emulsion suitable for topical application to human skin or hair comprises, in addition to water from 0.01 to 20%
by weight of a skin benefit ingredient, preferably a 2-hydroxyalkanoic acid having from-3 to 20 carbon atoms, or a salt thereof; from 0.1 to 20% by weight of polyoxyethylene-21-stearyl ether, as a principle emulsifier and from 0.5 to 70% by weight of an emollient oil.

Description

" ' .
" ; ~ "

~ J.3087 i COSM~TIC COMPOSITION

~, :
FI~LD OF INVENTION

3 The invention relates to emulsions which are suitable for topical application to skin or hair, more particularly to emulsions comprisin~ a 2-hydroxyalkanoic acid or a salt thereof or other skin benefit agents.

BACKGROUND AN~ PRIOR ART
,j .
The use of 2-hydroxyoctanoic acid in products for topical application to human skin has been proposed in ` EP-A 0 007 785 (Unilever). There remains, however, a problem in delivering this~acid to subcutaneous regions of the skin, where its benefit of increasing the extensibility of stratum corneum is maximised.
~, ` An attempt has subsequently been made, as described ;
i in EP-A-0 117 080 (Unilever), to improve the delivery of .~, :
.; ~
., ~, ., '~ .

:-, d 1 332~68 - 2 - J.3087 amphiphylic compounds such as 2-hydroxyoctanoic acid by the use of an emulsifier having an average HLB value of from 5 to 11, which is capable with water of forming a gel phase having an X-ray reflection of from 0.37 to 0.44, and which permits substantially no co-crystallisation with the amphiphylic compound. Although improved delivery of 2-hydroxyoctanoic acid has been demonstrated with compositions based on the emulsifier system disclosed in this reference, their shelf life is limited, in that syneresis tends to occur after storage at 45C lthe normal maximum storage temperature for testing stability) for only a few wee~s. Such limitations as to storage tability virtually rule out the possibility of employing such systems in products where manv weeks or months may elapse during storage prior to sale or prior to use by the consumer.

We have now discovered that bv selecting a special emulsifier not previously proposed for use with 2-hydroxyoctanoic acid and related substances, that emulsions can be prepared which are completely stable during storage at 45CC for at least 12 months, or longer at lower storage temperatures, and which also show excellent freeze-thaw stability following cooling to -22C, thus pro~Tiding an answer to a lonq felt need for superior storage stability characteristics. Furthermore, emulsions containing certain other skin benefit agents in place of or in addition to 2-hydroxyalkanoic acids such as 2-hydroxyoctanoic acid, also benefit from exceptional ; 30 storage stability when using the special emulsifier.

DEFINITION OF T~E INVENTION
' , Accordingly, the invention provides an emulsion suitable for topical application to human skin or hair, which comprises in addition to water:

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- 3 - J.3087 i) from 0.01 to 20~3 by weight of a skin benefit ingredient chosen from:

Retinoic acid Retinyl palmitate Ascorbic acid Ascorbyl palmitate Tocopherol Tocopherol acetate 3 10 Pyroglutamic acid and salts thereof ~ Amino acids ', Sunscreens ' Hyaluronic acid and salts thereof Perfluoropolyether ~ 15 Hydrocortisone acetate and : a 2-hydroxyalkanoic acid having from 3 to 20 carbon ' atoms, or a salt thereof; and mixtures thereof:
:
, 20 ii) from 0.1 to 20% by weight of . polyoxvethylene-21-stearyl ether as a principle , emulsifier; and ' iii) from 0.5 to 70% by weight of an emollient oil.
DISCLOSURE OF THF. INVENTION
.-.
,. The Emulsion : 30 The emulsion according to the invention will normally contain an aqueous phase and an oily phase and will . comprise a selected skin benefit ingredient, a special :; emulsifier and an emollient oil.

.`. 35 The emulsion preferably possesses a continuous aqueous phase in which case it is an oil-in-water ~:i emulsion, the aqueous phase comprising from 98 to 60~ by - 4 - J.3087 volume and the oily phase from 2 to 40% by volume of the emulsion.

Alternatively, the emulsion can possess a continuous oily phase, in which case it is a water-in-oil emulsion, the aqueous phase usually comprising from 25 to 70% by volume and the oily phase from 75 to 30% by volume of the emulsion. ~owever, the emulsion can also be a high internal phase water-in-oil emulsion, in which case the aqueous phase can compri~e up to 98% by volume of the emulsion, the nily ph~se then formina as little as 2% by volume of the emulsion.

The form of the emulsion, whether oil-in-water or ~ater-in-oil, will largely depend upon the average ~L~
value of the emulsifier(s) which is employed, values greater than 8 generally giving rise to oil-in-water emulsions and values of up to 8 generally givina rise to water-in-oil emulsions.
The Emulsion Inaredients (i) The skin benefit inaredient . .
The emulsion according to the invention comprises a skin benefit ingredient chosen from Retinoic acid Retinyl palmitate Ascorbic acid Ascorbyl palmitate Tocopherol Tocopherol acetate Pyroglutamic acid and salts thereof `~ ~
1 33~568 - 5 - J.3087 Amino acids ' Sunscreens j Hyaluronic acid and salts ther~of Perfluoropolyether 5Hvdrocortisone acetate and a 2-hydroxyalkanoic acid having from 3 to 20 carbon atoms, or a salt thereof; and mixtures thereof;

The emulsion can also comprise a mixture of two or more skin benefit ingredients.
:
Particularly preferred examples of amino acids include:
::
~ 15 glycine :` alanine valine ., leucine isoleucine phenylalanine tyrosine proline :: hy~roxyproline serine - 25 threonine `j cysteine cvstine ~ methionine i tryptophan .~ 30 aspartic acid x glutamic acid . arginine ~`. lysine, and `~ histidine.
. 35 ', :." ;:
.

` ^` - 1 332568 - 6 - J.3087 The amount of amino acid that can be employed in accordance with the invention will normally be from 0.01 to 20%, preferably from 0.1 to 10% by weight of the emulsion.
Particularly preferred examples of sunscreen active ingredients include:

p-Aminobenzoic acid Ethyl dihydroxypropyl p-aminobenzoic acid (such as Amerscreen P) Glyceryl p-aminobenzoic acid (such as Escalol 106) 2,4-Dihydroxy benzophenone (such as Uvinul 400) 2-Ethoxyethyl-p-methoxycinnamate (such as Giv ~an F) Di-ethanolamine p-methoxycinnamate (such as Parsol Hydro) 2-Ethylhexyl salicylate (such as Sun Arome WMO) Homomenthyl salicvlate (such as Filtrosol A) 2-Phenylbenzimidazole-5-sulphonic acid ~such as Eusolex ` 232) - 20 Octyl methoxycinnamate (such as Parsol MCX).
. 3-~4-Methylbenzylidine) camphor (such as Eusolex 6300) 2-Hydroxy-4-methoxy benzophenone (such as Eusolex 4360 ~utylmethoxydibenzoylmethane (such as Parsol 1789) 4-isopropyl dibenzoylmethane (such as Eusolex 8n20).

"
; The amount of the sunscreen active ingredient that can ` optionally be employed in accordance with the invention, as a therapeutically effective amount, will normally be from 0.01 to 10%, preferably from 0.1 to 5% and most preferably from 1 to 5% by weight of the emulsion.

Particularly preferred examples of 2-hydroxyalkanoic acids include 2-hvdroxypropanoic acid, 2-hydroxyhexanoic .

`"- 1 3325~8 - 7 - J.3087 acid and 2-hydroxyoctanoic acid. Further examples include 2-hvdroxy-N-butanoic acid, 2-hydroxydecanoic acid, 2-hydroxydodecanoic acid and 2-hydroxyoctadecanoiC acid.

Examples of salts of the above 2-hydroxyalkanoic acids are the sodium, potassium and triethanolamine salts, although it is to be understood that other metallic, ammonium or alkanolammonium salts are useful.

The emulsion according to the invention can comprise mixtures of 2-hydroxyalkanoic acids and/or salts and/or an acid soap complex thereof.

The most preferred 2-hydroxyalkanoic acid is 2-hvdroxyoctanoic acid or its acid soap complex having the empirical formula where M is a cation chosen from sodium, potassium and ammonium.

The amount of skin benefit ingredient present in the emulsion accordin~ to the invention is usually from 0.01 to 20%, preferably from 0.1 to 10% by weight of the emulsion.

(ii) The Principal Emulsifier The emulsion accordin~ to the invention comprises as the principal emulsifier polyoxyethylene-21-stearyl ether, also known as polyoxyethylene-21-stearyl alcohol, an example of which is Brij 721 (available from ICI). This emulsifier has an HLB value of about 15.5 and if used alone will yield an oil-in-water emulsion.
~ ~le~o~cs 7~ra~ rk - - 8 - J.3087 The amount of polyoxyethylene-21-stearyl ether present in the emulsion according to the invention is usually from 0.1 to 20%, preferahlv from 0.5 to 10% by weight of the emulsion.

(iii) ~he Emollient Oil ., The emulsion according to the invention comprises an emollient oil, that is an oily substance that is substantially insoluble, or only slightly soluble in water, and which usually constitutes the major ingredient of the ~ily phase of the emulsion.

Examples of emollient oils include the following:
` 15 Hydrocarbon oils and waxes: examples of which include, mineral oil, petrolatum, paraffin, ozokerite, microcrys~alline wax, polyethylene and perhydrosqualene q (squalane).
' 20 , 2. Silicone oils: examples of which include, dimethyl polysiloxanes, methylphenyl polysiloxanes.

3. Triglyceride esters: examples of which include, vegetable and animal fats and oils, such as caprylic and capric triglycerol (available as Migliol 812), wheatgerm oil, apricot kernel oil, avocado oil, sunflower seed oil, arnica oil, evenlng primrose oil and jojoba oil.

4. Acetoglyceride esters: examples of which include, acetylated monoglycerides.

- 5. Alkyl esters: examples of which include, methyl, isopropyl, and butyl esters of fatty acids; hexyl laurate, isohexyl laurate, isopropyl myristate, isopropyl - palmitate, flecyl oleate, isodecyl oleate, hexadecyl ..

:

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- 9 - J.3087 (isocetyl! stearate, diisopropyl adipate, diisohexyl adipate, dihexadecyl adipate, diisopropyl sebacate, lauryl lactate, myristyl lactate, and cetyl lactate.

6. Alkenyl esters: examples of which include, oleyl myristate, oleyl stearate, and oleyl oleate.

7. Fatty acids: examples of which include, lauric, myristic, palmitic, stearic, isostearic, hydroxystearic, oleic, linoleic, linolenic, ~ -linolenic, ricinoleic, arachidic, behenic, erucic, and lanolin acids.

8. Fatty alcohols: examples of which include, lauryl, myristyl, cetyl, hexadecyl (isocetyl), stearyl, isostearyl, hydroxystearyl, oleyl, ricinoleyl, behenyl and erucyl alcohols, and 2-octyl dodecanol.

9. Fatty alcohol ethers: examples of which include, ethoxylated lauryl, cetyl, stearyl, isostearyl, oleyl, and lanolin alcohols; and cholesterol; propoxylated cetyl, oleyl, and lanolin alcohols; and also polypropylene-15-stearyl ether.

lO. Ether-esters: examples of which include, fatty acid esters of ethoxylated fatty alcohols.
;

11. Lanolin and lanolin derivatives : examples of which ~-include, lanolin, lanolin oil, lanolin wax, lanolin alcohols, lanolin fatty acids and acetylated lanolin derivatives.

12. ax esters: examples of which include, lanolin (de-oiled wax fraction), beeswax, spermaceti, myristyl myristate, stearyl stearate.

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- 10 - J.3087 13. Beeswax derivatives: examples of which include, polyoxyethylene sorbitol beeswax. These are reaction products of beeswax with ethoxylated sorbitol of varying ethylene oxide content, forming a mixture of ether-esters.

14. Vegetable waxes: examples of which include, carnauba, candelilla.

15. PhoPholipids: examples of which include, lecithin and derivatives.

16. Sterols: Cholesterol, cholesterol fattv acid esters.

The amount of emollient oil present in the emulsion according to the invention is usually from 0.5 to 70%, prefera~ly from 1 to 60% bv weight of the emulsion.
;

Other emulsion ingredients (i) Secondary Emulsifiers The emulsion according to the invention can also comprise one or more secondary emulsifiers, in addition the principle emulsifier polyoxyethylene-21-stearyl ether.

Examples of secondary emulsifiers include:
HLB value BRIJ 72 (Polyoxyethylene-2-stearyl ether) 4.9 BRIJ 52 (Polyoxyethylene-2-cetyl ether) 5.3 `~ The presence of a secondary emulsifier can result in the formation of a water-in-oil emulsion, if the average HLB
of all emulsifers present does not exceed 8. The -`` 1 332568 - 11 - J.3087 preferred emulsions according to the invention are, however oil-in-water em~llsions.
.
The amount of secondary emulsifiers that optionally can be present in the emulsion according to the invention is up to 20%, preferably from n . 1 to 10% by weight of the emulsion.

(ii) Thickeners The emulsion accordina to the invention can also optionally comprise a thickener, examples of which ` include:

- 15 xanthan gum, such as Rhodopol 23, aluminium starch octenylsuccinate, such as Dry Flo starch, carboxyvinyl polymer, such as Carbopol 938, 940 & 941 . carboxymethyl cellulose, and ;, 20 hydroxypropvlmethyl cellulose.

The amount of thickener that optionally can be present in the emulsion according to the invention will depend upon which thickener is chosen, the amount being that conventionally employed as recommended by the respective manufacturer. Generally, the amount of thickener will be up to 10%, preferably from 0.1 to 5% by weight of the emulsion.
,. ~ . .
(iii) Skin Delivery Enhancers ` The emulsion according to the invention can also ;~ optionally comprise one or more substances to enhance ;~ deliverv of the skin benefit ingredient to the stratum ``~ 35 corneum.
, .
:; ~

.

- 12 - J.3n87 P~xamples of skin deliverv enhancers, which can function in a varietv of ways, include:

2-methyl propan-l-ol Propane-1,2-diol Ethyl-2-hydroxypropanoate ~exane-2,5-diol POE(2) ethyl ether Di(2-hydroxypropyl) e~her Pentane-2,4-diol POE(2) methyl ether Tetrahydrofuran ~utane-1,3-diol Propylene glycol dipelar~onate Octyl alcohol POE ester of olevl alcohol Oleyl alcohol Iauryl alcohol Dioctyl adipate Dicapryl adipate Diisopropyl adipate Diisopropyl sebacate Dibutyl sebacate Diethyl sebacate ~5 Dimethyl sebacate Dioctyl sebacate Dibutyl suberate Dioctyl azelate Debenzyl sebacate Dibutyl phthalate Dibutyl azelate Ethyl myristate Dimethyl azelate Butyl myristate Dibutyl succinate Didecyl phthalate ~-` ` `` ` 1 332568 - 13 - J.3087 Decyl oleate ~thyl caproate Ethyl salicylate Ethyl laurate 2-ethyl-hexyl pelargonate Isopropyl isostearate Butyl laurate Benzyl benzoate Butyl benzoate Hexyl laurate Ethvl caprate Ethyl caprylate Butyl stearate ~en~l salicylate ~,lycerol The amount of skin delivery enhancer, when employed -i in accordance with the invention, will normally be from 0.1 to 50%, preferably from 0.5 to 25%i and most preferably ~ from 0.5 to 15% by weight of the emulsion.
:
~ (iv) Perfume ~';
The emulsion according to the invention can also optionally comprise a perfume in an amount sufficient to make the emulsion acceptable to the consumer and pleasant to use. Usually, the perfume when present will form from 0.01 to 10% by weight of the emulsion.
` 30 (v) Further optional ingredients The emulsion according to the invention can also optionally comprise further ingredients in addition to those already described, such as colourants, whiteners, .. ....

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- 14 - J.3087 preservatives, antioxidants, or aerosol propellants, in amounts which are conventional in the cosmetics art.
pH

The emulsion according to the invention should normally have a p~ value of from 3 to 7, preferably from 3.8 to 5 and ideally from 4 to 4.5.

When the emulsion is an oil-in-water emulsion, the continuous phase being the aqueous phase, then the pH
value can be measured directlv from a p}l electrode placed in the emulsion.

When the emulsion is a water-in-oil emulsion, the continuous phase being the oily phase, then direct pH
measnrement of the emulsion is not possible. In this case, the pH value refers to that of the aqueous phase before emulsifyin~ in the presence of the oily phase.

PRODUCT FORMS AND PACKAGING
-The topical skin treatment emulsion of the invention can be formulated as a fluid, for example in a product such as a ~otion, with or without an applicator such as a " roll-~all applicator, or a propellant-driven aerosol device or a container fitted with a pump to dispense the composition, for example as a mousse or simply for -storage in a non-deformable bottle or squeeze container.
Alternatively, the composition of the invention may be solid or semi-solid, for example a cream or ointment, for use in conjunction with a suitable applicator, or simplv for storage in a tube or lidded jar.
:
More particularly, the viscosity of the emulsion will determine whether it is a lotion or-a cream. For example, x~

- 15 - J.3087 when the viscosity of the emulsion is measured using the ~rookfield Viscometer (lOrpm, measured at 20C usin~
spindles A to ~ as appropriate) then the following viscosity values provide a guide to the nature of the emulsion.

Viscosity tmPas) Description of emulsion up to 2,000 milk 2,000 to 5,000 thin lotion 5,000 to 8,000 normal pourable lotion 8,000 to 10,000 thick lotion*
]0,000 to 15,000 thin cream 15,000 to 30,000 normal cream 30,000 to 100,000 thick cream *dispensible from a squeeze container.

The invention accordinglv also provides a closed container containing a cosmetically acceptable composition as herein defined.

P~EPARATION AND PRODIJCT FORM OF THE EMULSION
., The emulsion of the invention can be prepared in the ` form of a lotion, cream, gel, ointment, solid stick or ` aerosol, or in any other form suited to administration topically to human skin.
.
Accordingly, the invention also provides a process for the preparation of an emulsion suitable for topical application to human skin or hair, which process comprises the steps of:

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1 33256~

- 16 - J.30B7 i. preparinq an aqueous phase, buffered to a p~ value of from 3 to 7, comprising a skin benefit in,gredient as herein defined, preferably a 2-hydroxyalkanoic acid or derivative thereof havinq from 3 to 20 carbon atoms, together with further water-soluble or water-dispersible ingredients as necessar~.

ii. preparing an oily phase comprisin~ emollient oil and polyoxyethylene-21-stearyl ether as emulsifier, together with other oil soluble inqredients;
.~
iii. adding the oily phase prehea~ed to a temperature of at least 70C to the aqueous phase, also preheated to a temperature of at least 70C, with high shear mixing to form an emulsified mixture, iv. cooling the emulsified mixture to a temperature of ' from 35 to 50C and adding the aqueous buffer with ,; low shear mixing;

v. cooling to a temperature of not greater than 35C and ~' adding preservatives and perfume as re~uired with ~, further mixing;
., to obtain emulsion as herein defined.

' FVIDENCE TO DEMONSTRAT~ SUPERIOR STORAGE
STABILITY OF EMULSIONS

, 30 As has been stated earlier, the emulsions of the invention `,~, exhibit superior stability during storaqe at 45C to any '`~ other emulsion containing skin benefit ingredients, such as 2-hydroxyalkanoic acids.

; 35 This superiority was demonstrated using a formulation comprising the principal emulsifier, namely, ` 1 332568 - 17 - J.3087 polyoxyethylene-21-stearyl ether, compared with two similar formulations, in which this principal emulsifier had been replaced bv other emulsifiers.

The basic lotion formulation contained the following ingredients 2-hydroxy alkanoic acids % w/w 2-hydroxv propanoic acid 4.0 2-hydroxy octanoic acid 1.0 Emulsifier as selected* 1.8 Emollient oils lanolin derivative 0.95 wheat~erm oil 0.05 isopropyl myristate 1.0 cetyl palmitate 2.0 wax 2.0 fatty alcohol 1.2 silicone oil 6,0 Thickeners aluminium starch octenyl succinate 3.0 xanthan gum 0.1 Deliver~T enhancer , ~ butane-1,3-diol 9.45 : 35 .

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`` ` 1 332568 - 18 - J.3087 j Other ingredients whitener 0.15 ' preservatives 0.36 '~ 5 water to 100 . Three lotions were prepared based on the above formula:
these were identical except for the emulsifiers which were as follows:
t~ 1 0 ~ Lotion Emulsifier*
:i .
;` A Brii 58 (pol~roxye~hylene-20-cetYl ether) s B Brij 78 (polvoxyethylene-20-stearyl ether) . 15 C Brij 721 (po1~oxyethylene-21-stearvl ether) :
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- 19 - J.3087 Results The fcllowing results were obtained after storage:

(i) Stability data The results of storaqe tests at -22C(4 F/T cycles), 20C, 35C and 45C on the three basic lotion models are given in Table 1.
Tah]e 1. Stabilit~ Data for Lotion Models Freeze-Thaw Cycles (x4) Lotion at -22C 20C 35C 45C
;, _______________________________________________________ ____ A Stahle Stable Stable for Stable for ' after for 18 months 1 mth then 1 mth then :- 20 4X oil on then ` surface separated ? --------____________________________________________________ B Stable Stable Stable for Stable for after for 18 months 3 mths then 2 mths then . ~X separated separated ~` ____________________________________________________________ ~ Stable !Stable for 20 Stahle for Stable for after months 13 months 13 months 4X (storage ongoing) _ _ _ _ . ` ' . , ~ . .
~`' . ' , ~
. `? ' . .`

- 20 - J.3087 Table 1 shows that all three lotions survived four freeze-thaw cycles at -22C. With regard to the storage data, there appears to be a trend in the stability conferred by the emulsifiers on the o/w emulsions such that, that containing Brij 721 was clearly far more stable, even when stored at 45~C, than those containing either Brij 78 or Brij 58.

This confir~.ed that Lotion C in accordance with the invention exhibited unexpected superior storage characteristics.

(ii) ~icrostructure of Lotions The microstructure of each lotion was studied 24 hours after preparation, and then after 3 months storage at 20C, and after 6 months storage at 20C. The results obtained are given in Table 2.

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-` 1 332568 - 21 - J.3087 Table 2.
Results from Microstructure Studies (maanification X 100) , _________________________________________________________ Lotion 24 hr after After 3 mths After 6 mths preparation storage at 20C storage at 20C
_________________________________________________________ A Emulsion Flocculation Islets of coalesced appeared and some oil droplets; some stable coalescence phase separation.

B Emulsion Flocculation Coalescence of ~ appeared of oil oil droplets `~ 15 stable droplets _________________________________________________________ , C Emulsion Microstructure No gross changes in : appeared unaltered. microstructure and ` stable. no evidence of Particle flocculation or , size smaller coalscence.
- than for Lotions A
:
`` or B
------------------_-__-_________________ __ ~' The microstructure results reported above provide further evidence to support the finding that the most sta~le `? lotion was Lotion C in accordance with the invention.
(iii) Rheoloqy of lotions All three lotions A, B and C showed some thickening during ~torage see Table 3. Of the three, Lotion C showed the `~ 35 least change after six months storage. The results obtained are given in Table 3.
, . ......................................................................... ..
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`` 1 332568 - 22 - J.3087 Table 3 Viscositv Data using ~rookfield Viscometer .
(at 20C, lOrpm using Spindle B) _______________________________________________________ VISCOSITY
_ ________ _________________________ 24 hr after After 6 mths Lotionspreparation storage at 20C

(mPas~ (mPas) _________________________________ ~ 1200 8400 The viscosity measurements reported above indicate that I,otion C, whose initial viscosity was ideal to enable it to be used as a normal pourable lotion, showed the least change in viscosity during prolonged storage, whereas the comparative Lotions A and B, both of which were too thin ¦ for use 24 hours after preparation, showed unacceptable I increases in viscosity during storage.

~vidence to Demonstrate Increase in Extensibility of Stratum Corneum .

The ability of the emulsion according to the .
invention to enhance the delivery to skin of 2-hydroxyoctanoic acid, as an example of the 2-hydroxy alkanoic acids, or salts thereof, as herein defined, was measured in terms of the increase in extensibility of heat-separated quinea pig foot pad stratum corneum following contact with the emulsion, as compared with another emulsion which did not contain polyoxyethylene-21-stearvl ether.

`` 1 332568 - 23 - J.3087 Tn this experiment, pieces of guinea pig foot pad stratum corneum, equilibrated at a relative humidity of 64%, were immersed in each emulsion or control for 3 hours at 20C, and then removed, blotted dry and re-equilibrated at the same rela~ive humidity. The extensibility of each piece of guinea pig foot pad stratum corneum was measured before and after this treatment in an extensiometer according to the method described in EP-A-0 007 785.

Results The results of this experiment are tabulated below:

Table 4 In Vitro Extensibility Data ~20C, 64% RH) Lotion Extensibility ratio (+2 Standard errors) 6.6 (+1.8) C 8.1 (+1.4) The above results indicate that there is an 23~ increase in extensibility in vitro when the principle emulusifier, as herein defined, is employed (i.e. Lotion C in accordance with the invention), compared with control Lotion A containing an ordinary emulsifier. This confirms significantly enhanced delivery to the stratum corneum of 2-hydroxyoctanoic acid using the emulsion of the invention as compared with a control emulsion.

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``` 1 3325~

- 24 - J.30 EXAMPLES

The invention is further illustrated by the follo~ring examples.
Example 1.

This example illustrates an oil-in-water skin cream according to the invention.

% w/w Skin benefit ingredients 2-hydroxypropanoic acid 4.0 2-hvdroxyoctanoic acid 1.0 Principal emulsifier polyoxyethylene-21-stearyl ether 2.4 ~ .
Secondary emulsifier polyoxyethylene-2-stearyl ether 2.6 ~:
~ mollient oils ,`'! polyoxypropylene-15-stearyl ether 8.0 fatty alcohol 4.0 i` 25 silicone oil 0.1 i, ~elivery enhancer ~ butane-1,3-diol 5.0 ,:, 30 Other ingredients ~` preservative 0.36 pH adiustant 3.36 ~' perfume 0.1 ! water 69,08 , 35 100.00 .i.
~' ~
. The cream had a pH value of 4.

.

`` 1 332568 :

- 25 - J.3087 Example 2 Thi~ example illustrates an oil-in-water skin lotion according to the invention.

% w/w Skin benefit ingredients 2-hydroxy propanoic acid 4.0 2-hydroxy octanoic acid 1.0 Principal emulsifier polyoxyethylene-21-stearyl ether 1.8 Emollient oils lanolin derivative 0.95 wheatgerm oil 0.05 isopropyl myristate 1.0 cetyl palmitate 2.0 wax 2.0 fatty alcohol 1.2 :.
silicone oil 6.0 . .
Thickeners Aluminium starch octenyl succinate 3.0 xanthan gum 0.1 Delivery enhancer butane-1,3-diol 9.45 : 30 Other_ingredients : whitener 0.15 preservatives 0.36 pH adjustant 3.36 perfume 0.1 water 63.48 100.00 The lotion had a pH value of 4.
., 1 33256~

- 26 - J.3087 .

Viscosity: Brookfield Viscometer, lOrpm, Spindle B
measured at 20C.

5 Storage time: 24 hrs 6 months viscosity (in mPas) 6000 7200 "
., .
. ~

- 27 - J.3087 Example 3 This example illustrates on oil-in-water fluid skin cream according to the invention.

~ w/w Skin benefit in~redlents 2-hydroxy propanoic acid 4.0 2-hydroxy octanoic acid 1.0 lC
Principal emulsifier polyoxyethylene-21-stearyl ether l.B -~mollient oils lano~.in derivative 0.95 wheat germ oil 0.05 cetvl palmitate 2.0 isopropyl myristate 1.0 wax 3 0 fatty alcohol 1.2 - silicone oil 5.0 Thickeners .
aluminium starch octenyl succinate 3.0 xanthan gum 0.1 '~
- Delivery enhancer butane-1,3-diol 9.45 30 Other ingredients :
whiteners 0.15 preservative 0.36 pH adjustant 3.36 ~' perfume 0.1 water 63.48 100.00 The emulsion had a pH value of 4.

' .

28 - J.3087 Viscosity: Rrookfield Viscometer, lOrpm, Spindle B
measured at 2QC.

5 Storage time: 24 hrs 13 weeks Viscosity (mPas) 5800 22,000 ;.
:, :

:~` 1 332568 - 29 J.3087 Example 4 !

This example illustrates an oil-in-water skin cream according to the invention. %wlw ~ Skin benefit ingredients ; 5 2-hvdroxy propanoic acid 4.0 2-hydroxyoctanoic acid 1.0 Principle emulsifier polyoxyethylene-21-stearyl ether0.94 Secondary emulsifier polyoxyethylene-2-stearyl ether 0.86 Emollient oils lanolin derivative 0.95 - whe~t germ oil 0.05 isopropyl myristate 1.0 cetyl palmitate 2.0 ozokerite wax 3.0 fattv alcohol 1.2 silicone oil 5.0 Thickeners -. aluminium starch octenyl succinate 3.0 xanthan gum 0.1 ` Delivery enhancer ` ~utane-1,3-Ziol 9.45 Other ingredients`

30 whitener 0.15 preservatives 0.36 pH adjustant 3.36 perfume 0.1 water 63.48 100.00 The cream had a pH value of 4.

- 30 - J.3087 Viscosity: Brookfield Visc~meter, lOrpm, Spindle D
measured at 20C.

5 Storage time: 24 hrs Viscosity ~mPas) 50,000 .

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``` ` 1 332~68 - 31 - ~ ;

Fxample 5 This example illustrates~ an oil-in-water skin ~ n accordin~ to the invention.
s ...~

Skin benefit ingredient hydrocortisone acetate Principal Emulsifier polyoxyethylene-21-stearyl ether Secondary Emulsifier 15 polyoxyethylene-2-stearyl ether 0 Emollient ~ils isopropyl myristate 2.,~
cetyl palmitate ~ 3!1, 20 wax 2,~'s~
fatty alcoh~
silicone oil St.

Thickener 25 xanthan gum 0 i~
.~ :
Deliverv enhancer ., - butane-1,3-diol 13 .~
!
30 Other ingredients whitener t.
preservatives 0 water to 100 " 35 The cream will have a pH value of from 3 to 7.

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- 32 - J.3087 Example 6 This example illustrates an oil-in-water skin lotion according to the invention.
: 5 ~ w/w ~kin benefit in~redients Tocopherol 0.20 Ascorbic acid 0.30 Principal Emulcifier polyoxyethylene-21-stearyl ether 1.80 Emollient oils `` 15 avocado oil 0.50 arnica oil 0.50 isopropyl myristate 2.00 ~` cetyl palmitate 2.00 wax 2.00 1 2n ~atty alcohol 1.20 `. silicone oil 6.00 ~ .
Thickeners alumi~ium starch octenyl succinate 3.00 25 xanthan gum 0.l0 Delivery enhancer butane-1,3-diol 7.50 3n Other Ingredients whitener 0.20 preservatives 0.36 perfume 0.10 water to 100 `35 : The lotion will have a pH value of from 3 to 7. `
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`` ~ 1 3 3 2 5 68 _ 33 _ J.3087 ExamPle 7 This example illustrates an oil-in-water emulsion according to the invention.

% w/w Skin benefit in~redients retinyl palmitate 0.10 octyl methoxy cinnamate 3.00 10 butylmethoxydibenzoylmethane 1.50 ; Emulsifiers polyoxyethylene-21-stearyl ether2.40 polyoxyethylene-2-stearyl ether 2.60 Emollient oils wheatgerm oil 0.10 ` caprylic/capric triglvcerides 5.00 ! silicone oil 2.50 `. 20 evening primrose oil 0.40 : elivery enhancer glycerol 5.00 25 Other ingredients ~ allantoin 0.50 :~ preservatives 0.36 ` perfume 0.15 water ` to 100%
` 30 ~ ` :
~ The emulsion will have a pH value of from 3 to 7.

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~ `' - ~ 1 332~68 - 34 - J.3087 Example 8 This example illustrate an oil-in-water emulsion according to the invention.
S
% w/w Skin benefit ingredients ~, L-proline 0.1 octyl methoxycinnamate i Emulsifiers ~a polyoxyethylene-21-stearyl ether 3 polvoxyethylene-2 stearvl ether 2 15 Emollient oils stearyl alcohol polyoxypropylene-15-stearyl ether 10 ~ilicone oil 0.5 evening primrose oil Delivery enhancer propane-1,4-diol 4 Other in~redients 25 preservative and perfume qs water to 100 This emulsion will have a pH value of from 3 to 7.

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Claims

1. An emulsion suitable for topical application to human skin or hair, which comprises in addition to water:

i. from 0.01 to 20% by weight of a skin benefit ingredient chosen from Retinoic acid Retinyl palmitate Ascorbic acid Ascorbyl palmitate Tocopherol Tocopherol acetate Pyroglutamic acid and salts thereof Amino acids Sunscreens Hyaluronic acid and salts thereof Perfluoropolyether Hydrocortisone acetate, and a

2-hydroxyalkanoic acid having from 3 to 20 carbon atoms, or a salt thereof; and mixtures thereof.

ii. from 0.1 to 20% by weight of polyoxyethylene-21-stearyl ether, as a principle emulsifier; and iii. from 0.5 to 70% by weight of an emollient oil.

2. An emulsion according to claim 1, in which the amino acid is chosen from:

glycine alanine valine leucine isolencine phenylalanine tyrosine proline hydroxyproline serine threonine cysteine cystine methionine tryptophan aspartic acid glutamic acid arginine lysine, and histidine and mixtures thereof.

3. An emulsion according to claim 1, in which the sunscreen is chosen from:

p-Aminobenzoic acid Ethyl dihydroxypropyl p-aminobenzoic acid Glyceryl p-aminobenzoic acid 2,4-Dihydroxy benzophenone 2-Ethoxyethyl-p-methoxycinnamate Di-ethanolamine p-methoxycinnamate 2-Ethylhexyl salicylate Homomenthyl salicylate 2-Phenylbenzimidazole-5-sulphonic acid Ethylhexyl p-methoxycinnamate 3-(4-Methylbenzylidine) camphor 2-Hydroxy-4-methoxy benzophenone Butylmethoxydibenzoylmethane, and

4-isopropyl dibenzoylmethane.

4. An emulsion according to claim 1, in which the 2-hydroxyalkanoic acid is chosen from 2-hydroxypropanoic acid, 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid and mixtures thereof.

5. An emulsion according to claim 1, 3 or 4, in which the 2-hydroxyalkanoic acid salt is chosen from the sodium, potassium and triethanolamine salts.

6. An emulsion according to claim 1, 3 or 4, in which the amount of the skin benefit ingredient is from 0.1 to 10% by weight of the emulsion.

7. An emulsion according to claim 1,3 or 4, in which the amount of polyoxyethylene-21-stearyl alcohol is from 0.5 to 10% by weight of the emulsion.

8. An emulsion according to claim 1, 3 or 4, in which the emollient oil is chosen from:

polyoxypropylene-15-stearyl ether dimethylpolysiloxanes lanolin cetyl alcohol stearyl alcohol wheatgerm oil isopropyl myristate cetyl palmitate evening primrose oil arnica oil avacado oil caprylic and capric triglycerols ozokerite wax, and mixtures thereof.

9. An emulsion according to claim 1, 3 or 4, in which the amount of the emollient oil is from 1 to 60% by weight of the emulsion.

10. An emulsion according to claim 1, 3 or 4, which further comprises a secondary emulsifier chosen from:

polyoxyethylene-2-stearyl ether polyoxyethylene-2-cetyl ether, and a mixture thereof.

11. An emulsion according to claim 1, 3 or 4, which further comprises a delivery enhancer chosen from:

butane-1,3-diol, glycerol propane-1,4-diol, dibutyl sebacate, and mixtures thereof.

12. An emulsion according to claim 1, 3 or 4, which further comprises a perfume.